Clarify striding in usage message
Comment from Jay Heinzelman from testing GRB 1.0:
- --stride? How does this work? Do the resolutions of the data really not lend to this showing much difference? I didn't find a combination of image size and stride that yielded visible or file size differences. I tested with -S 1 and -S -1. Those seemed like the only two options from how I read the documentation. -S 1 will used the full resolution, and -S any negative number will try to reduce the number of lines in the processed dependent on the quick look image size. (At first I thought if I used -6 I'd get every sixth line/element, but after testing and reading the doc closer I didn't think that was the case.) I wanted to point this out in case there is a problem here.
Graeme's reply (second paragraph is relevant to this ticket):
You can specify a positive stride to override the default auto-stride, but in my testing there was little effect on the plots until you actually exceed the auto-stride value and the image gets coarser. My theory is that the Python plotting routines are doing striding internally, so as far as image quality it doesn't really matter how much you stride on input (up to the point where you have fewer input pixels than the image size).
Maybe the action here is to clarify in the usage message that stride should be specified as a positive number, with a special value of -1 indicating auto-stride.